FIB-4 Calculator
Calculate the FIB-4 index from age, AST, ALT and platelet count to estimate the risk of advanced liver fibrosis.
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About the FIB-4 Calculator
The FIB-4 index is a simple blood-test-based score used to estimate the likelihood of advanced liver fibrosis, especially in people with fatty liver disease or chronic hepatitis. It combines age, AST, ALT and platelet count. This calculator is for education and should not replace medical advice.
How to use it
- Enter the patient's age and the AST, ALT and platelet values from a recent blood test.
- Press Calculate FIB-4.
- Read the score and risk range, then discuss it with a clinician.
FIB-4 formula
FIB-4 = (age × AST) ÷ (platelets × √ALT), with age in years, AST and ALT in U/L and platelets in 109/L.
FIB-4 interpretation
| FIB-4 score | Risk of advanced fibrosis |
|---|---|
| Below 1.3 (below 2.0 if age 65 or older) | Low |
| 1.3 to 2.67 | Indeterminate |
| Above 2.67 | High |
A score in the indeterminate range is usually followed by another test, such as elastography. Results can be affected by age and other conditions.
Frequently asked questions
What is the FIB-4 index?
A calculation using age, AST, ALT and platelet count that estimates the risk of advanced liver fibrosis.
What is a normal FIB-4 score?
A score below 1.3 suggests low risk of advanced fibrosis. In adults 65 and older, a cut-off of 2.0 is often used.
Does a high FIB-4 mean I have cirrhosis?
No. It signals a higher chance of advanced fibrosis and usually leads to further testing.
What units does the calculator use?
Age in years, AST and ALT in U/L and platelets in 10⁹/L, the same number as K/µL.
Is this medical advice?
No. It is an educational tool. Always consult a doctor about your lab results.
Last reviewed: November 2026. Educational use only. A FIB-4 score is not a diagnosis. Talk to your doctor about liver health.